Metachrome dyeing procedure



Tatented Aug. 22,

UNITED STATES PATENT OFFICE METACHROME DYEING PROCEDURE No Drawing.Application May 2'7, 1947, Serial No. 750,886

10 Claims.

This invention relates to improved metachrome dyeing processes.

In the past there have been four general procedures employed in dyeingwith metallizable dyes. The first utilizes preformed metallized dyes andrequires the formation of the metallized dye before it is introduced.into the dye bath. Practically all of the metallizable dyes may beutilized in this process, but it is subject to a number ofdisadvantages. The dye is not very efficiently used, the dye bath ispoorly exhausted, and the color value is not as high as desirable insome cases.

The second process is referred to as an after chrome or top chromeprocedure in which the fabric is dyed with metallizable dyes and thensubjected to an after treatment with a solution of a compound of themetal to be introduced into the dye molecule. As the name implies, thedye is applied the same as an acid dye, and it requires an extra processand extra time for the formation of the metallized complex.

The third procedure is the so-called bottom chrome process in which ametal compound is first deposited in the textile fiber and then the dyeis applied and the metaliized complex forms in the fiber. Here againthis process is an extremely long one requiring several steps.

The fourth procedure is the so-called metachrome process in which themetallizable dye and the compound of the metal to be introduced are bothpresent in the dye bath at the start and the metailized dye is formedboth in the fiber and in the bath itself and not introduced as apreformed compound.

The metachrome process presents many advantages. However, in many casesthe dye is not eiiectively utilized when dyeing basic nitrogenous fiberssuch as the natural animal fibers, Wool, silk, and the like or syntheticfibers of similar type from casein, polyamides, and so forth. Certaindyes give good uniform liber'penetration in a yarn, and others penetrateonly some of the fibers. The dyes which do not penetrate all of thefibers or are destroyed during the dyeing operation, particularly in thecase of heavier shades, have, therefore, been considered unsuitable foruse in the metachron'ie process and have required resort to the processstarting out with the preformed inetallized dye or the top or bottomchrome processes With'their attendant disadvantages.

According to the present invention it is found that markedly increasedstrength and levelness of dyeing is obtained if three factors arepresent in the process. These three factors are:

let: The presence of a salt of an alkaline earth metal.

2nd: A water dispersible surface active composition containing at leastone cationic surface active agent.

3rd: The pH of the dye bath is sufficiently high initially so that rapidchromation is prevented or retarded, and during the dyeing process thepH is progressively lowered until final chromation results.

With certain dyes any one of the three factors referred to above willefiect some improvement either in color value or levelness, but withcertain other dyes, both of these improvements in dyeing characteristicsare not obtained with metallizable dyes unless all three of the abovereaction conditions are present, and the present invention contemplatesonly processes in which all three factors are efi'ective.

The alkaline earth metal'salts or salts to be used are not in the leastcritical. Any of the common soluble salts may be used. The difierentalkaline earth metal salts will vary to some extent in their effect, andthis variation is not the same with all metaliizabie dyes. In general,best results are obtained with magnesium salts, magnesium sulfate beingparticularly desirable, by reason of its cheapness, ready availabilityand the excellent results which it gives in the process of the presentinvention. Accordingly magnesium sulfate represents the preferredalkaline earth metal salt, though in its broader aspects the inventionis not limited to its use.

The reason for the improved results obtainable wi'th alkaline earthmetal salts, and particularly the increased strength of dyeing whichfollows their use, has not been completely determined and, therefore,the present invention is not intended to be limited to any theory of theaction of the alkaline earth metal salts. Certain observations withcertain dyestuffs make it appear very probable, that at least with somedyestuffs, magnesium or the other alkaline earth metal salts actuallyform metal complexes with the dye,\which complexes are only stable insolutions of high pH. Some of the dyes change their color verystrikingly when they are introduced into a dye bath containing thealkaline earth metal salt. Such a great change in color, which is againreversed as the dyeing proceeds and the pH fails to sufiiciently lowValues, makes it almost certain that there is an actual chemical changein the dye molecule. The conditions unexplanation is advanced,therefore, as probable in the case of some at least of-"the'metallisabledyes which may be used in the processv of the present invention.

It is an advantage of the invention: that the amount of the addedalkalinecearthrmetal salts.

is not critical. It should, however, be realized that the action appearsto be in no sensecatalytic. Relatively substantial amounts of alkalineearth metal salt must be added. Normally the amount added is at least,equal to the weight of the.,dye,-althQugh-.this figure does notrepresenta sharp or critical dividin line. ;S maller-amounts will.exert effect,but -onewhich rapidly diminishes as the amount of salt becomesinadequate. .It;has..been found; that the amount of alkalineearth.:meta1 salt-maybe advantageously correspondingly greater than theWeightmf the dyestuff. .Eor. example, .the .use..of, five times as muchalkaline earthmetal .salt gives excellent. results,- and:sincethealkaline earth .metal .salts, are relatively. cheap. chemicals-titis. preferred, to .use them in excess of the weight of thedyestufi-,..although the inventionds notbroadly limited to thispreferred amount.

The second factor requires .a:.water. dispersible surface activecomposition containing-at least one cationic surface active agent. It isalso .desirable that any insoluble reaction products of the cationicsurfaceactive' agent be likewise dispersible. Thisdispersibility of thesurface active composition may be'effected in-several'ways.For-instance; the cationic surface active agent may becolloidized-eithei =by itselfor in combination with the dyestuff.or-alka-line earth metal salt -or-with --the 'chromating mordant.methods --.are I described in--Patent--*No. 2,434,178 issued January-6,i948 to-Royerand-'Amick. -Another method ofbbtainingwaterdispersibi-lity-is to associate-the cationic surface'active agentwith nonionic surface active'agents as is described in' the Millson andRoyer application SerialNo 42p;50e, filed November 26,1941.

The presentinvention is not concerned with the particular methods ofachieving dispersibility of the surface active component, this formingthe subject matter of the applications above referred to. .On thecontrary, the presentinvention is concerned only with water dispersiblecationic surface active compositions when associated with the othertwofactors of the processof the present invention, namely, the presenceof the alkalineearth metalsalt, and the initial high pH of the dye bath.

.The third factor, namely, high initial pH, is also not a. criticaloperating procedure. It will vary quite widely with different dyestuffsand with difierentfabrics. In general it will never be lower than 5.5andthe upper limit is from about 8 to 9.5. Theupper limit is. defined,not So much bythe reaction, itself, as by the fabric, because it isnecessary to maintain the pH below the point at which thebasic,nitrogenous fibers areiciu q, e era he ni hpfis be chosen uf i ientyhish tar tmrd-imtim chr- These mation. With dyestuffs with which itseems probable that a complex is formed with the alkaline earth metalsalt, the pH initially should be high enough so that the complex, ifthere be one present, is not decomposed until the dyeing of thefiber'has proceededto the desired extent.

.,As the fibers, are dyed-.andxthe normal-heating of the bath continues,there is a definite lower- ,ing of pH, the bath becoming more and moreacid. When the pH gets low enough, both dyeing and chromation proceedmore rapidly, and a final dyeing of "high strength and good levelnessresults. Thus. it -.is.--now possible to obtain deep.shades,.-.such.-;as\adeep chrome black, by a true metachrome process.

.While, as vpointed out above, the pH of the dye bath is lowered by thedyeing procedure itself, probably because of a reaction of the basicnitrogenous fiber with the alkali present, this lowering is usuallyinsufficient, hence in the majority of cases.it-is;desirable;to.'add--small .amountsof acid or acid salts as the dyeing proceeds.:Preferably the .acid: is added in.parts- .1after. onehalf houraboiling,and' after an,hour s boiling. The-exact amountwf addition -of.=acid and.the timeand.portionsare not critical but optimum results .will vary alittle with different colors. This is entirely consistent with. normaldyeing practice .wvhereit .is usually necessaryto make some changes.insthe dyeing time, temperature, and pI-Iwith difierent dyesandsdifierenhfibers in order.to get the best results. .The same typeofadjustment is employed in the proeesszofthe present ,inventio .:which isan advantageas .the dyer. doespnot have. to learmnewtechniques.

.While .-the .process of the .present .invention giyes, importantimprovementindyeing. withordinary dyes.:by.:the metachrome.method,producing stron shades with .axhigh .degreeof .levelness.-andexcellenceolifastness to. lightand ful1ing,.a. further; advantagalies.in .the fact that -certain chromable dyes, .which .are rdyeable. in;the .metachrome-process only when the woolhhas been modifiedby oneofgtne.various non-feltingtreatments ysuch ,as chlorination, can ,be dyed bythe present;p10,0$ on, ordinary wool. This ,is important as it opens 111a new, field for thesedyes. In addition, to the improved resultsobtained by the process of the present invention, a, further advantage.lies in the material saving whichcan be effected in the amountofchromium containing salt used. In ,iavorable cases this may amount to 40or The invention will ,be described in greaterdetail in conjunction withthe following specific examples. Theparts are by weight.

Example 1 "One part of the condensation pro'ductof octadecyl uanidinebicarbonate and ethylene oxide (1 mole to 6 moles) aredissolved in anexcess of organic solvent, e. g., ether. 20 parts .of Epsom salts are.added and the ether evaporated slowly with constant stirring to depositthe cationic agent on theEpsom salts base. .Finally theproduct isvacuumdried. When the drying is completed, the product is grindaole. 52.5parts of this product is dry-blended with 3 parts of powdered K2C1207.togive a mordant. Twelve percent of thisproduct (based on the weight ofthe wool) is used with 2% of the ordinary commercial chrome types togive a satisfactory dyens. The. dyeinais. made as. follows:

2% dye (C. I. 202) predispersed, in boiling water was admixedwith'12% ofthe mordant and a sumcient amount of ammonia or ammonia and ammoniumsalt such as ammonium dihydrogen phosphate, to produce a pH of about 8.5to 9.0 in a 400ccfvolurrie, sufficient Water being used to make thenecessary dilution.

A 5 gram woolen piece or skein is pre-wet with water and entered intothe dye bath at 120 F. The dye liquor is gradually brought to the boilin hour with frequent turning of the wool to insure uniform dyeing.Boiling and turning are continued for hour, after which 2% of 28% aceticacid is added. After another half-hour on the boil, 4% of 28% aceticacid is added. Dyeing is continued at the boil for a third half-hourmaking a total dyeing time of two hours.- The color of the dyed skein isblue-black and the dyeing has good fastness and is very level.Ordinarily this color can be dyed satisfactorily only by the verycumbersome top or bottom chrome method.

Example 2 37.5 parts of corn dextrine made by dextrinizing corn starchwith hydrochloric acid, 37.5 parts of Epsom salts, 3.75 parts of thecationic agent of Example 1, 4.5 parts of KQCI2O'1 and about parts ofwater are wet-blended in a Warner-Pfleiderer mixer until uniform. Thisgives a thick plastic magma. The product is then transferred to enameledtrays and dried in a vacuum dryer, ground and screened through a 140mesh screen. 12% of this product is substituted for the material inExample 1 and dyeings are carried out in the same way with essentiallythe. same results.

The chrome equivalent amount of KzCrOx can be used in place of theK2CI2O'1.

Example 3 The product of Example 2 is used in making a dying of the dyeC. I. 652, using the dyeing formula of Example 1. This dye gives anexcellent color value which is superior to that obtained by ordinarymetachrome dyings or even top chrome dyeings.

Example .4

500 parts of the dextrine of Example 2 .and 100 parts of thecondensation product of octadecyl guanidine bicarbonate and ethyleneoxide (1 mole to 6 moles) are blended in a Werner-Pficiderer mixer withsufiicient water to give a stifi plastic magma. The well mixed materialis then transferred to enameled trays and vacuum dried. It is thenground and screened through a 140 mesh screen. parts of this product, 24parts of 100- mesh Epsom salts, and 6 parts of 140 mesh KzCrzO'z aredry-blended to give a mordant. 6% of this mordant and 2% of 28% NH4OH(both on the weight of the wool) and 100 mg. of the dye having C. I. 203are dyed on a 5 gram woolen skein as in Example 1. The dyeing obtainedis blueblack, has excellent fastness properties and is fiber level.

Example 5 and screened through a 140 mesh screen producing a colloidizedmordant.

A dye bath is prepared as follows:

0.1 g. dye (C. I. 202) predispersed in boiling Water, approximately 2%of 28% NH/LOH to give a pH not greater than 9.5

12% colloidized mordant 400 cc. dye bath volume A 5 gram woolen piece orskein is pre-wet with 'water and entered into the dye bath at 120 F.

The dye liquor is gradually brought to the boil in hour with frequentturning of the wool to insure uniform dyeing. Boiling and turning arecontinued for /2 hour after which of H2SO4 is added. Dying is continuedat the boil for a second half hour, after which of H2SO4 is added.Dyeing is then continued for a third half-hour at the boil making atotal dyeing time of two hours.

The color of the dyed skein is blue-black and the dyeing has goodfastness and is fiber level. Ordinarily this color can be dyedsatisfactorily only by the very cumbersome top or bottom chrome method.

The same results are obtained if the potassium bichromate is substitutedby a chromium equivalent amount of potassium chromate.

Example 6 The dyeing procedures of the preceding example is repeatedusing the dye C. I. 652 instead of the dye of Example 5. The dye givesan excellent color value which is superior to that obtained by ordinarymetachrome dyeings or top chrome dyeings.

Example 7 500 parts of the dextrine of Example 2 and parts of thecationic surface active agent described in Example 5 are colloidized ina Werner- Pfieiderer mixer with just suificient water to give a stiffplastic magma. The product is then dried, ground and screened asdescribed in Example 5. 30 parts of the screened material aredry-blended with 100 parts of Epsom salts and 6 parts of potassiumbichromate.

A dye bath is prepared with 13.5% of the above mordant and 2% of 28%ammonia (both on the .'eight of the wool) and 2% of dye having C. I. 203are added, and the dyeing is carried out by the procedure of Example 1or Example 5. The dyeing produces a blue-black shade which is fiberlevel and has excellent fastness properties.

Example 8 A dye bath is prepared as described in Example 4 using 7% ofmordant and 6% of dye. Wool is dyed in the bath and builds up with theincreased amount of color to give a very dark, blue-black shade ofexcellent fastness properties and fiber levelness.

Example 9 500 parts of the dextrine of Example 2 and 100 parts ofcationic surface active agent as described in Example '7 are colloidizedand vacuum dried. 30 parts of the product are blended with 35 parts of100 mesh Epsom salts and 8.3 parts of potassium bichromate until auniformly blended product is obtained.

7% of the mordant produced and 2% of 28% ammonia together with 2% of thedye C. I. 292 are made into a dye bath. Wool is dyed in skein form asdescribed in the foregoing examples, and astrong green dyeing isobtained having excellent fastness properties.

Example 2 parts of the dyeCt'IrZM; andonepartof'the condensationproduct-of*2-mols of polyethylene oxide (molecular weight 4000) and ,1mol of the .dimerized'. acidobtained by heat treating gsoya bean acidsand distilling off the monomericacids are dry blended. 3%oflthissproduct;6%ofthe mordant of Example 4 and:2% of:28%rammoni'a aredissolved in 400 parts of water and wool is dyed therein bythe,proce'dure of Example 1. A good, bright orange'color'is obtained andthe dyed wool has good fastness and levelness.

.Example 11 A dye'bath is prepared: with l'partof the .dye having" the iColor Index #203 (pure presscake) idispersed'in.20001partsofgboilingwater. This-is then diluted with an equal amount. of watercontaining'6 parts of the'mordant of Example' 4'' and? parts of. 28ammonia. Fifty .parts of pre=wet wool'arethenientered' and dyed asinExample 5. A black shaderof' goodfiberlevelness is obtained.

Example 12 The procedure of Example eis-repeated, except thedyeinggis'made -on-synthetic'casein fiber and the dyeis nitro aminophenol diazotized and coupled with-metaphenylene diamine which isdiazotized and coupledto=5-sulfo a-naphthol, Prototype 14. obtained.

Example: 13

Theprocedureof Examplee is repeated,- except the dye is C.I. -652 andthematerial'is nylon. A strong, bright red shade is, obtained.

Example 14 .The procedure of the-preceding example is repeated exceptthedye is C.--I..292. 'A good slate .greenshade is obtained which iscommercially satisfactory.

Example 15 50.,parts of the. dextrine of Example -2'.and 10 parts of thecondensation..product -of.octadecyl guanidine bicarbonate .andethyleneoxide (5-1) are colloidized-andvacuum dried. .Thisaproduct .isathen.ground, screened throughma 100 mesh screen,..and dry blended with 40parts of the commercial dye havingColor- Index. N o. v203.

.A batchof. woolen fabric is dyed in a commer cial dye, kettle asfollows:

10% of the above blendedcolor ammonium acetate 3.3% Epsom salts 0.7%potassium dichromate .The cloth was entered into the .dye kettle, and.wetv outwith water. If necessary, vthe cloth.-is treated to make itneutral, after which the :treating water was discharged from the kettle,refilled, heated to 120 F. and the above ingredients added 'in the ordergiven. The starting pH was about 5-.5 as determined by Universalindicator paper. The dye liquor was slowly heated to. 207 to 208 F. atwhich time the .pH wasjabout 6.0 and runabout loyminutes, after which 2%of 28% acetic acidwas ied'on and the pH idropped to'5'.0. After dyeingfor an additional i0 minutes, 2% of 28%-acetic. acid wasaddeda secondtime, .and thepHiremained about'5;0.

When the dyeing was .completed,-the woolen "fabric was dyed a; .black.color. having. goodfast- "ness and levelness.

An excellent brown dyeing is "A :dyeing composition is prepared 'fby dryblending 60-parts'of the colloidized cationic surfaceactive agent of thepreceding example-with 40 parts-of the yel1ow"dyestuff"preparedbydlazotizing sulfanilic-acid and coupling to 2=hydroxy-i-amino benzoicacid.

A' dyeingis prepared as follows:

,All weights'are based uponthe weight :of .the

.wool to be dyed 5% of the blended dye prepared as 'in themecedingparagraph 10% ammonium sulfate 0.6%v potassium dichromate Bath ratio: -1

-The-starting pH'of this'dye solution wlll'vary from a pH" of5.0-6;0depending uponthe-previoushistory of the-wool and how thoroughly it hasbeen neutralized after the" preceding operation.

The bath is brought 'to. the boil gradually in 30 minutes, boiled 30minutes, after which 3% of the 28% acetic a'cidis added. Afterana'dditional 30 minutes at the boil, a secondadditl'on of 3% ofi28%acetic acid isadded and the boilm continued for another"30 minutes.

Wool dyed as above'has a brilliant yellow color, showing excellentlevelne'ssand good 'fa'st- 'ne'ss properties.

Example]? .The, procedure of Example 1 is'repeated except the dye C. I..1085 is ,used instead of C. L202 of Example ,1. The dyeing produces -.a.blueblack shade which is levelaand'has excellent fast- :nessproperties.

.Examplell A dye bath is preparedzasifollows, all weights being based onthe wool.

2%.dye having Color Index No..-202 2 %.;of .28 ammonium hydroxide 1%. ofthe non-ionic agentpreparediyrreactlng ,;2 moles of poly-ethylenezoxide(M.-W.-.4000) and 1 mole of the dimerized acidmbtainemby heat treatingsoya bean acids and distilling on the monomeric acid 0.5%. of .the.cationic-activeagent--of Example -No. 1 10% Epsom salts 0i6.%..potassiumdichromate The dye bath isthen made up to 40000. with water, after whicha 5-gram 'woole'n piece or ske'in'is .p're-Wet and dyed as'in ExampleNo..-1 orNo. 5'andthe strength and shade of the dyed piece .isrgenerallylikethat obtaine'dirom Eia'm'ple No. 1

Example 19 The procedure: of Example No; 18 is repeated except thedye-having Color-Index 'No. 652 is used instead of the dyehavingColor'InderNo. 202. 'Wool dyed by-this color and procedure givesexcellent strength and levelness, usually superior to theconventionaltopchrome methods of dyeing.

'ExampZe'ZO The procedure :of Example- No. .18. isxrepeate'd except thedye havinglColorIndex No. 9835 used in place of thedyehaving ColorlndexNo. 202 Wool dyed'bythis color and.procedure has-er- :cellent strengthand fiberlevelness, .beingtequal usually to .a top :chrome :d-yeingas;made by the conventional methods.

Example 21 The procedure of Example No. 18 is repeated except the dyehaving Color Index No. 1085 is used in place of the dye having ColorIndex No. 202. Wool dyed by this color and procedure has good colorvalue and fiber levelness.

Example 22 The procedure of Example No. 18 is repeated except the dyehaving Color Index No. 201 is used in place of the dye having ColorIndex No. 202. Wool dyed by this dye and procedure is stronger andbrighter than wool dyed with an equivalent amount of dye which is dyedby the conventional top chrome procedure.

Example 23 The procedure of Example 18 is repeated except the dye havingColor Index 274 is used in place of the dye having Color Index No. 202.Wool so dyed has excellent color value, is bright and has good fiberlevelness.

Example 24 400 parts of yellow corn dextrine and 100 parts of thecationic surface active agent described in Example 1 are intimatelymixed and vacuum dried as described. parts of this material arethen-dissolved in 95 parts of water to give a 1% solution of thecationic surface active agent. A dye bath is then prepared as follows:

2% of the dye having Color Index No. 203 predissolved in 100 ml. water300 ml. of water 2% of 28% ammonium hydroxide 2.5 ml. of the 1% solutionof cationic surface active agent described above.

% Epsom salts 0.6% potassium bichromate A 5-gram pre-wet wool skein isthen dyed therein, using the dyeing procedure on Example No. 1 and thestrength and shade of the dyed wool is very fiber level and is usuallystronger than equivalent dyeings made by the conventional top chromeprocedure. Magnesium acetate or magnesium chloride may be substitutedfor the Epsom salts.

The addition of the ammonium hydroxide generally changes the pH to 9-9.6depending upon the pH of the water added to the dyebath. The shade ofthe dye having Color Index No. 203 is plum colored or reddish after theaddition of the water to make up the dyebath, particularly if distilledwater having a pH lower than '7 is used. After the addition of theammonium hydroxide, the shade of this color becomes greenish-blue. Uponthe addition of the Epsom salts the color of the dye solution becomes acherry red, although there is no appreciable change in pH. During thesubsequent dyeing, this dyebath exhausts very rapidly, much more so thanwhen a similar dyeing is made except the Epsom salts is omitted.

Example 25 The procedure of Example 24 is repeated, except 10% ofcalcium nitrate .4 B is substituted for the Epsom salts of Example 24.The shade of the dyed wool is slightly grayer than that obtained whenEpsom salts is used. The addition of 10% of the calcium nitrate .4: H2Obased on the weight of the wool to the dyebath likewise caused noappreciable change in pH but did cause the blue green shade of the dyesolution to become a brighter red. l

10 Example 26 The procedure of Example 24 is repeated except 10% ofbarium nitrate is used instead of the Epsom salts. The wool dyed fromthis bath is slightly bluer and brighter than that dyed by the procedureof Example 24.

Example 27 The procedure of Example is repeated except the dye havingColor Index No. 652 is used instead of the dye having Color Index No.203. A good strong red dyeing is obtained. If desired, the calciumnitrate may be replaced with strontium chloride.

Example 28 The procedure of Example 18 is repeated exactly except 0.5%of the surface active agent, tertiary amine hydroacetate, preparedaccording to U. S. P. 2,200,815 is used instead of the surface activeagent prepared by the condensation of octa decyl guanidine bicarbonateand ethylene oxide (6:1) which was used in Example 2. W001 dyed withthis procedure shows good strong blueblack color with good penetration.

iii

Example 29 The procedure of the preceding example is followed exactlyexcept the surface active agent, cetyl pyridinium chloride, is usedinstead of the tertiary amine hydroacetate of the preceding example. Agood strong bright blue-black dyeing is obtained.

Example 30 The procedure of the preceding experiment is repeated exceptthe surface active agent, cetyl trimethyl ammonium bromide is usedinstead of the cetyl pyridinium chloride. A good strong brightblue-black dyeing is obtained.

Example 31 The procedure of Example 18 is repeated exactly except thesurface active non-ionic agent of Example 18 is replaced by 1% of betahydrotriethoxy-propyl-lauramide. A good bright blue black dyeing whichshowed excellent penetration is obtained.

Example 32 The procedure of the preceding example is repeated exactlyexcept the beta-hydro-triethoxypropyl-lauramide is replaced with 1% ofp-hexadecyl phenyl ether of polyethylene glycol.

Example 33 The procedure of Example 18 is repeated except the non-ionicsurface active agent of Ex-. ample 18 is replaced with the condensationproduct of stearyl alcohol with 8 moles of ethylene oxide liquified with30% E20. Wool dyed by this procedure gives a bright blue-black shadeshowing excellent penetration and ood fiber levelness.

Example 34 l l shades, this gives the best results. However, in somecases, particularly with dark-shades .such

as maroon; brown,- navy and black; it is. some times advantageous 'toaddsmallamounts of ad-.

ditional -bichromates, ior example, .3 to :.5%., to

the bath after it has beenrboiling for about onehalf hour or so. Theadditional chromium makes the dark shades somewhat'richer and in manycases improves fastness' towet finishing. The

addition of small amounts of the chromatesto the bath after the dyeinghas proceeded for some time is therefore included'in the scope of. thepresent invention.

The improved results obtainabletby, meansof the present inventionare notalways the same with each dye. In many cases improved strength andpenetration result: in other cases, the levelness is better while withsome dyes; improvements in both characteristics are observed; The degreeof improvement in various characteristics varies with the dye. Ingeneral, theprocess of the present invention shows less'irarkedadvantages with some yellow dyes than-with dyes of other shades.

In the examples. dyestuff'mixtures havebeen colloidized by working'in arelativel stiff paste with carbohydrates. suchasdextrine and dried at alow temperature so that the individual particles on contact withwaterdispersedrapidly without violent agitation to form a colloidalsolution. Such product have been described in'the specification ascolloidized. This term is used in the claims in no other sense.

We claim.

.1. A. m t d o dyeinrz'wh h compr se subjectingsubstant ally unmetalized basic nitrogenous fibers to the action of a -dye-bath:-formed. by mxing a-c romable dye. a soluble chromium-.

containin sa t. a sol ble alka neeart m t l salt, a water-disnersihlesurface-a ct ve c mposition containin at le st one cation c surfaceactive ag nt. water, and sufli'cient alk l to make the bath alkalineand'to cau e said dye to react w th said a kal ne earth metal saltto'form an alkaline earth meta complex of said dye andinsufficient tomateriallv damage the-fibers; partially dyeing said fibers from saidcomplex, gradually lowering t e pH of said hath toqarpoint' tomaterially damage the fibers, partiallydyeing said fibers from saidcomplex, gradually lowering the pH of said bath to a point wheredecomposition of said complex and 'chromation take place, and completingthe dyeingat said lowered pH.

3. A method of dyeing which comprises sub jecting substantiallyunmetallized basic nitrogenous fibers to the action of 'a dye bathformed bymixing a chromable dye, a soluble chromium containing salt, asoluble alkaline earth metal salt, a water-dispersible surface activecomposition containin at'least'one cationic surface activeagent, water,and suificient alk l 170 1 3 the bath alkaline ancl'to cause said dye toreact With-.said valkaline'earth metal salt ,t0..f0rm-an alkalineeanthmetalicomplexof saiddye and in: sufficient tomaterially damagethefibers,.par.-. tiallydyeingsaidfibers .from said complex, grade uallyloweringthe-pH ofsaidbathby the addition of successive small portions ofacid to a point where decompositionof said complex and chromation takeplaceyandcompleting the dyeingat said lowered pH..-

4. A method of dyeing which comprises: subjectingxsubstantially-unmetallized. basic nitrogenous=fibers to the-action of afdye bathformed.

bymixing a chromable dye; a soluble chromium containing salt,-magnesiium sulfate, a waterdispersible surface-active compositioncontaining at least one cationic surface active agent, water, andsufiicient alkali to make the bat-halkalinc andito cause said dye toreactwith said alkaline.

earth .metalpsalt toform an alkalineearth metalcomplexof saiddyeandinsuificient tc materially damage the fiberspartially dyeing'saidfibers from said complex, gradually lowering the pH of said bath by theaddition of successive small portions of acid to-a'point wheredecomposition ofrsaidcomplex and chromation take place, and. completingthedyeing at saidlowered pH.

5: Ainethod of dyeing which comprises subjecting-substantiallyunmetallized 'basic nitrog-:

enousfibers to'the action of a dye bath formed.

by mixing a vcln'on'iable dye, a soluble chromium containingsalt,.a.-solub1e alkaline earth metal salt, awater-dispersiblelsurfaceeactive composition containing at least onecationic surface active agent, water, and suificient. alkali to makethe. -.bath.,alkaline, but .with apI-lnot greater than 9.5, and to causesaiddye to react with said alkaline earth metal salt to form. an.alkaline earth metal complex of said and-.imufiicient to materiallydamage the fibers, partially dyeing said fibers from said complex,gradually lowering the pI-lof said bath to a point where decomposition-ofsaid complex and chromation take place, and completing-the dyeing atlowered :pH.

6.-'A-method -of dyeing which comprises subjecting substantiallyunmetallized basic nitrogenous fibers to the action of a dye bath formedby mixing a chr mable dye, a soluble chromium containing salt, magnesiumsulfate, a waterdispersible surface-active composition containing atleast one cationic surface active agent, water, and sufficient alkali tomake the bath alkaline, but. witha'pI-I not greater than 9.5, and tocause said dye to react withsaid alkaline earth metal salt to form:analkaline earth metal complex of said dye and insufiicient tomaterially damage the -fibers,'par-tially dyeing saidfibers from saidcomplex, gradually lowering the pH of said bath toua point wheredecomposition of said complexand chromation takeplace, and-completingthe dyeing at said lowered pH.-

7; A method according to claim 1 in which the cationic surfaceactive-agentis a condensation product of octadecyl guanidine andethylene oxide.

8. A-method according to'claim 2 in whichthe cationic surface activeagent is .-a condensation product of octadecyl guanidine and ethyleneoxide.

9.- A method according to claim 4 in which the cationic surface activeagent is a condensation product of octadecyl guanidine and ethyleneox--ide.

10. A method according to claim 6 in which the cationic surface activeagent is a condensation 2,520,105 13 14 product of octadecyl guanidineand ethylene oX- OTHER REFERENCES ide.

Theory and Practice of W001 Dyemg by C. L. Bird, published in London in1947 by the Society of Dyers and Colourists, pages 87, 88.

WILLARD WATKINS 5 Application of Coal Tar Dyestuffs, by C. M. Whittaker,published in London 1919 by Balliere, REFERENCES CITED Tindall and Cox,pages 59-61, inclusive.

The foliowing references are of record in the Applicatign of Dyestuffsby Matthews file 0f t S P t 10 published in New York by John Wiley 8:Sons,

UNITED STATES PATENTS 1920. Pages 356-358.

Metachrome Method of Dyeing, by C. H. A.

Number Name Date Schmitt, article in Amer. Dyes. Reporter for 941,399Winslow Nov. 30, 1909 J 26 1939 P336 P341 1,511,359 Onnertz Oct. 14,1924 Pages 2,434,178 Royer Jan. 6, 1948 15

1. A METHOD OF DYEING WHICH COMPRISES SUBJECTING SUBSTNATIALLYUNMETALLIZED BASIC NITROGENOUS FIBERS TO THE ACTION OF A DYE BATH FORMEDBY MIXING A CHROMABLE DYE, A SOLUBLE CHROMIUM CONTAINING SALT, A SOLUBLEALKALINE EARTH METAL SALT, A WATER-DISPERSIBLE SURFACE-ACTIVECOMPOSITION CONTAINING AT LEAST ONE CATIONIC SURFACE ACTIVE AGENT,WATER, AND SUFFICIENT ALKALI TO MAKE THE BATH ALKALINE AND TO CAUSE SAIDDYE TO REACT WITH SAID ALKALINE EARTH METAL SALT TO FORM AN ALKALINEEARTH METAL COMPLEX OF SAID DYE AND INSUFFICIENT TO MATERIALLY DAMAGETHE FIBERS, PARTIALLY DYEING SAID FIBERS FROM SAID COMPLEX, GRADUALLYLOWERING THE PH OF SAID BATH TO A POINT WHERE DECOMPOSITION OF SAIDCOMPLEX AND CHROMATION TAKE PLACE, AND COMPLETING THE DYEING AT SAIDLOWERED PH.